Prior art reveals that this second sub-assembly is most often constituted by deformation- and abrasion-resistant layers, which can be decorated using a rigid plastic material such as ABS (acrylonitrile butadiene styrene), polyamide, or a metal such as aluminum.
Nevertheless, the use of these materials does not make it possible to produce special shapes on the top of the ski, except by adding to the weight of the assembly or by altering the mechanical properties of the ski, e.g., stiffness, an alteration that is not always desirable.
FR 2,589,073 proposes the creation, around a mechanical assembly of a ski, of a U-shaped shell made of a hard polyurethane plastic material applied by spraying, molding or RIM (reaction injection molding). This construction allows the manufacture of skis having differing complex shapes, while retaining a single mechanical sub-assembly with carefully-designed, advantageous properties. However, this sub-assembly offers limited decorative possibilities. Furthermore, overly aggressive blows of the ski edges may seriously damage this covering layer, and the resistance of this covering is not optimal over time.